The disclosed embodiments of the present invention relate to dealing with transmission collision between two wireless communication terminals, and more particularly, to methods and apparatuses for detecting transmission collision and/or alleviating transmission collision.
Regarding a half-duplex communication system such as a WiFi system, a wireless communication terminal is allowed to perform only one of a transmission (TX) task and a reception (RX) task. Therefore, when two wireless communication terminals linked to each other are operated under the TX mode to transmit packets to each other, a TX collision happens. As none of the wireless communication terminals is operated under an RX mode, one of the wireless communication terminals fails to receive packets transmitted from the other of the wireless communication terminals. Thus, both of the wireless communication terminals have to re-transmit the packets (i.e., transmit retry packets), resulting in degradation of the system throughput.
Taking the WiFi system for example, an access point (AP) and a station (STA) are initially synchronized in time domain. Thus, time points separated by a fixed period (e.g., a 9 us period) would be used as TX start points of the AP and STA. One conventional means for avoiding the undesired TX collision is to use the clear channel assessment (CCA) mechanism. In general, the CCA mechanism is only capable of detecting an on-going packet transmission. However, as both of the AP and STA may leave the RX mode and enter the TX mode at the same time point due to the aforementioned TX timing synchronization, the CCA mechanism of either of the AP and STA is disabled in the beginning of the packet transmission. In other words, in a case where both of the AP and STA transmit packets at the same time, the CCA mechanism is disabled and fails to detect the occurrence of TX collision.
Thus, there is a need for an innovative design for detecting the TX collision and/or alleviating/avoiding the TX collision.